Question 147101
THe perimeter of a rectangle using length and width is given by,
{{{P=2*L+2*W}}}
For your case, the length is 5 ft longer than twice the width.
1.{{{L=5+2*W}}}
You also know that 
2.{{{P=2*L+2*W=320}}}
Solve eq. 1 for 2W and substitute into eq. 2,
1.{{{L=5+2*W}}}
{{{2*W=L-5}}}
Substitute into eq. 2 and solve for L.
{{{2*L+2*W=320}}}
{{{2*L+(L-5)=320}}}
{{{3*L-5=320}}}
{{{3*L-5+5=320+5}}}
{{{3*L=325}}}
{{{L=325/3}}}
{{{L=108.3}}}
From eq. 1, 
{{{2*W=L-5}}}
{{{2*W=108.3-5}}}
{{{2*W=103.3}}}
{{{W=51.7}}}
Check your answers.
{{{2L+2W=320}}}
{{{2(108.3)+2(51.7)=320}}}
{{{216.6+103.4=320}}}
{{{320=320}}}
True.
{{{L=5+2W}}}
{{{108.3=5+2(51.7)}}}
{{{108.3=5+103.4}}}
{{{108.3=108.4}}}
True (off because of roundoff error).
Your answers led to true statement.
They are good answers.